Underreamer



G. A. MONTGOMERY.

UNDERREAMER.

APPLlc/mon FILED lum: 1k |920.

1 ,368,96 1. Patented Feb. 15, 1921.

3 SHEETS-SHEET l.

G. A. MONTGOMERY.

UNDEHREAMER.

APPLlc/mou FILED JUNE r. 1929.

1,368,961. Patented 11811451921.

3 SHEETS-SHEET 2.

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fg Afro/Mfr MLM G. A. MONTGOMERY.

umoeammaa.

APPLICATIDN HLD )UNE 192D, 1,368,961 Patented Feb. 15, 1921.

3 SHEETS-SHEET 3. /9

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y uNi'rED 4srrarEs GUSTAVUS A. MONTGOMERY, GUIBERSON CORPORATION,

PATENT OFFICE.

UNDEBREAMER.

LSG/8,961.

Specification of Letters Patent.

Patented Feb. 15, 1921.

Application filed June 7, 1920. Serial No. 887,129.

To all whom t may cof/wem.'

Be it known that I, GUs'rAvUs A.. MoN'rooMnRr, citizen of the Republic of Finland, residing at Dallas, in the county of Dallas and State of Texas, have invented certain new and useful Improvements in Underreainers, of which the following is a specification.

This invention relates to new and useful im rovements in underreainers.

n important result soughtl by the invention is the provision of greater bearing areas for the bits, whereby more amplified surfaces are offered in sustaining the end thrusts, than is usually present in the reamers now in use. A further aim of the invention is to strengthen the bit at the intersection of the bit-body and the shank, thus eliminating a weak point, where fracture often occurs. The invention also involves longitudinal and radial bearing surfaces of an extensive nature, whereby the bits are braced against transverse, lateral and longitudinal strains and are more substantially supported. Another important point involved in the invention is a spring actuated expanding mechanism4 for the bits which includes a centrally located expanding element co-acting with the bits and the reamer body in such a manner as to produce a more efficient and satisfactory operation. P

ln carrying out the invention a reainer body is provided at its lower extremity with a tongue which constitutes an expanding element. A pair of bits are mounted substantially on each sideof the tongue so as to swing in planes parallel to the tongue, and are provided with channels receiving the tongue; whereby guides are had for the bits while the saine are being expanded; and also whereby a brace is provided which prevents the bits from collapsing during the reaming operation and further braces them against torsional and lateral strains.

The bits are pivotally supported and are connected by a transverse member. Re-

silient means Jfor retracting and thus ex panding the bits, is connected with the bits through their pivotal support. The tongue co-acts with the resilient means in expanding the bits and this is one of the important eatures of the invention. Thebody is provided with diametrically opposite recesses or sockets in its outer sides for receiving shanks formed integral with the bits, the transverse member referred to engaging said Shanks. It is preferable to taper the sockets and the Shanks so as to lit therein so that said Shanks will wedge in the sockets when the bits are expanded, thus taking the strain ofi' of the resilient retrac-ting means until the bits are displaced from the sockets.

In fact it has been found advantageous to make the contacting surfaces at a number of points in the reamer, tapering2 whereby repairing is facilitated by cutting back the transverse surfaces so that pla between the tapering surfaces is thus ta en up. The

vreadiness with which a reamer may be repaired without rebuilding the same adds considerable to its value.

A very im rtant feature in a. preferred form of the invention is found in tapered splines disposed lon itudinally of the body for receiving each it. These splines amplify the bearing surfaces so as to take lateral and tangential strains as well as end thrusts. Another point in favor of the spline is that when the Shanks become loose in the sockets the bits may be removed, hea-ted and. driven on the splines, thus taking up play 4and tem orarily restoring the reamer to good con ition.

Another point of novelty resides in tapering the expanding tongue and channels of the bits to correspond therewith so that when said bitsare expanded they will have a tendency to wedge onto the tongue, however this is not an essential feature. 1t has been found advantageous to include a spring pressed runner which is radially proJected from the body to travel on the inside of the casing and to operate a latch normally holding the bits contracted and the spring actuating means in restraint; but arranged to withdraw the latch to release the spring actuating means when the reainer has been lowered below the casing, whereby the bits are expanded. M

l'n order to prevent loss of the bits. in case all of the sustaining elements which support the bits should be broken, safety projections are provided on the tongue so as to be received in recesses in the bits when the lati displacement of the parts.

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ter are released and drop down. These projcctions are located so as to arrest the bits before the dove tails can disengage from their ,f grooves, thereby preventing lateral This is a very enporiant feature.

l prefer to employ a central mandrel within the body and provide the same with a cross head which engages in counter bores in the hits; together with a. reti-acting spring surrounding the mandrel and means for holding the bits in pivotal relation to the mandrel, but the invention is not to be conined to this particular consti-notion.

A very important structural feature is the strengthening of the intersection of'. the shank and bit and this is aecomlilished by building up the hit above its shoulder; thus inrreasing the material at this point and reduring the liability of breakage.

'lheiinvention will he more readily under stood from a reading of the following speciiieation and by reference to the accompanying drawings, in which an example of the invention is shown, and wherein:

Figure 1 is a View ot' a realner constructed in aceordance with my inventioina portion of the reamer being in section and a portion in elevation and the bits beingr expanded,

Fig. 2 is a similar view showing the bits contracted,

Fig. 3 is a view at right angles to Fig. 1, the major portion being in section and the lower portion being in elevation,

Fig. 4 is an elevation of the rearner-body, the upper portion being in section,

Fig. 5 is a .longitudinal sectional view of the reanier body,

Fig. 6 is a cross-sectionall view on the line (3-6 of Fig. 5,

Fig. T is an under side view of the i-eamer with the bits contracted,

Fia4 S is a similar view with the bits eX- pa nded,

Fig. 9 is a Cross-sectional view on the line fyi-9 of Fig, 4,

Fig. l() is a vross-scetional 1li-Agni' Fig. 5,

Figs. 11 to 14 inclusive are details of one of the hits showing all four sides of the same,

Fig. is a plan view of one of the bits,

Fig. 1G is a detail of the pivot bolt,

l `ggz li' is a detail of the mandrel.

Fig. is another view of the mandrel at ang-les to Fig. 1T, and

i9 is an elevation of the wedge tool used in collapsing the bits.

in the drawings the nun'ieral 10 designates an elongated reainer body having a tapered screwll'ireaded socket 11 at its upper end for receiving the lower end oi the coupling ,member (not shown) by which the reamer is eonnerted with its operating means. The body has ilattened portions 12 on opposite view on the line of the body.

sides, whereby a Wrench grip is provided for turning the body in connecting and disconnecting,r it from its coupling.

An expanding element' in the form of a tongue 13 is formed integral with the body at its lower end. The tongue s located centrally of the body. Un each side of the tongue and parallel thereto are vertical grooves 14, which latter are angular in crosssection and flare downwardly and'outwardl with relation to the sides of the tongue as 1s best shown in Fig. 5. It is desirable, but not essential, to taper or reduce the tongue in a downward direction whereby it is given a` Wedge shape. Radial recesses l5 extend outwardly from the grooves to the outer surface of the body and in conjunction with said grooves, form dove-tail sockets 'as is clearly shown in Fig, 6, 9 and 10.

It Will be noted that the tongue extends below the body proper and artic-ularly, has its vertical edges perpendicular. The tongue is less in width than the diameter of the body and 'is comparatively thin. The body is cut back from its lower end to form a shoulder 16 at one side of its recess 15 on each side of the tongue, thus removing the metal to the plane of, and eo-ineident with the flat side of the tongue. Q11 the Side of the tongue. a spline 17 extends downwardly on each side The inner edge of each spline to the adjacent groove 14 and is tapered in harmony therewith. The outer edge of each spline is also ta )ered accordingly. It will be noted that t e grooves 14 flare downwardly in tivo directions, the radial projection of the splines conforming to one fiare and the vertical edges conforming to the other flare.

A pair of bits 18 are each provided with an offset shank 19 extending vertically. This provides each bit With a shoulder Z0 extending laterally with relation to the inner face of the slmnl as is best shown in Figs. 11 and 13. In order to strengthen the bits each is built up laterally to one side of its shank by forming a boss 21 in the angle at the intersection of the bit body or cutter portion and thus producing an e evated shoulder 22 on top of the boss. Each bit has its outer surfare rounded and is provided at its lower end with an arcuate cutter 23 projecting outwardly. The under surface of each cutter is beveled inwardly and upwardly. This gives two bevels to the cutters, thus permittiny`r the same to be readily sharpened.

The bit body is cut away under each shank and formed with a web 24 having one side face in a vertical plane contiguous to theinner faces of the boss 21 and the shank 19 thereof. The inner edge of each web is inis contiguous clined upwardly to the center of the bit.

and 15. It will be seen that in each bit the shank 19 and bit bod which includes the Wing 25, are tied toget er by the boss 21 and the web 24, and these arts brace the bits in the line of radial Strain incidental to their expansion and operation; thereby prevent ing breakage at this point.

Each shank is tapered upwardly on each side and its inner face is also tapered or inclined upwardly. The Shanks are shaped to (it the socket formed by the grooves 14 and recesses 15, thus each exhibits a dove-tail shape in` plan. This causeseach shank to have vertical ribs 26 along each side, flush with the inner face and engaging in the grooves 14.

The tongue 13 has a central longitudinal slot 27 extending upwardly from opposite the lower end of the body l() to the tops of the dove-tail sockets, where it meets a central counter bore 28 which merges at its upper end into a main bore 29. At the intersection of the bores 28 and 29 an annular shoulder 3() is formed. The main bore terminates at the socket 11. A central mandrel 31 disposed in the main bore extends down through the counter bore` 2S and into the slot 27. At its lower end the mandrel carries a tubular cross-head 32 projecting on each side of the tongue 13 from the siot. Transverse openings 33 are provided v through the upper ends of the Shanks and each opening has a countersunk seat 34 in the inner face of the shank. The seats receive the ends of the'crosshead. whereby the bits are pivotally supported by the crosshead and the mandrel.

For taking up the play between the4 parts a cross bolt 35 is passed through the openings 33 and the erosshead. Each shank has on its outer face a vertical key seat 36 bisecting an annular recess 37 surrounding the outer end of the opening 33. As is shown in Figs. 3 and 16 the bolt 35 has its screw threaded end engaging inan annular nut 38 which is seated in one of the recesses 3? and is formed with a peripheral lug 3S) project ing into the seat 36, wherebyY the nut is countersunk below the outer surface of the shank and is held against rotation. The bolt has a head 40 on its opposite end engaging in the recess 37 of the other shank. The bolt head has an angular wrench socket 41 at its center intersected by diamctrical apertures 42. A wrench (not shown) is inserted in the socket 4l and the bolt screwed into the nut. When the parts arc tight a cottor pin 43 is passed through the apertures from the recess 3G, whereby the bolt is fastened against rotation.

A. washer 44 surrounding the mandrel rests on the shoulder 30 and supports the lower end of a coiled spring 45 encircling the mandrel within the main bore. A cap `46 is screw threaded on the upper end of the mandrel and contines a washer 46 on top of the spring. An expansion spring is em-y ployed and tends to force the mandrel upwardly, thereby drawing the Shanks into the sockets.

Referring again to the bits it will be noted that the inner faces of the same engage the sides of the tongue 13. Each wing 25 has an upwardly flaring channel 47 conforming to the taper of the sides of the tongue, the bottom of the channel being perpendicular like the ed res of the tongue. In the inner face of each boss 21 a sufnp 48 is provided: The sumps are shaped and proportioned to snu ly receive the splines 17, which may be we ged into said sumps. The channels receive the vertical edges of the tongue and act as guides.

When the bits arenlowered the sumps are carried below the splines thus permitting the bits to swing inwardly and collapsed as is shown in Fig. 2. The lower end of the tongue is curved and the upper endsof the channels are rounded at 47 thus when the bits are collapsed the rounded ends 47 ride under the under corners of the rounded end of the tongue.- The rounded ends 47 thus assist the shoulders 20 in riding under the tongue, whereby the tongue takes the u ward thrust of the spring 45. To permit the hits to be lowered and collapsed` it is necessary for the Shanks to swing and therefore one corner of the upper end of each shank is out off at 49 and a notch 50 is cut. in the other side of the shank near its center. The sockets of the head have beveled portions 49 receiving the ends 49 when the shanks are drawn into the sockets.

When the bits are lowered and the rounded ends 47 ride under the tongue; the beveled ends 49 permit thev Shanks to swing, the notches 50 receiving the lower corner of the reamer body. as is shown in Fig. 2. The bits have their outer surfaces shaped so as to ride true down the casing, when collapsed. Then the hits are collapsed the cutters 23 are well within the diameter of the reamer and thus cannot strike or catch in the joints. In order to collapse the bits it is necessary to force the mandrel downward against the tension of the spring 4.5 and for this purpose a wedge 51 (Fig. 19) is inserted through slots 52 in the body 1U so that its lower edge bears on the top of the cap 4G. By drivlng the wedge transversely through the body 10 the mandrel is forced downward and the bits carried downward until their shoulders 2() can be swung inward under the tongue. The wedge is left in place until the bits are inserted in the casing.

While the rounded outer surfaces of the. bits would ride on the'inner surface of tlfe casing and hold themselves collapsed, I prefer to use other means. lnA the side of the reamer body l provide a vertical cavity 53 in which a radial runner 54 is mounted. rlhe runner has coiled springs 55 projecting from its rear edge, bearingI against the baek wall of the cavityI and tending to force the. runner outwardli'Thhrunner has a depending pin 56 engagingin the slotted shank of a spring pressed latch 5T extendiut?r inward in the body 1U. rPhe mandrel has an annular lshoulder 58 which is engaged under the latch when the mandrel is depressed to collapse the hits. So long as the runner is in the casing it cannot more out-` ward sulliciently for its pin to withdraw the latch. However just as soon as the runner rides below the easing the runner is freed, so that its springs 55 will force it outward far enough to withdraw the latch 5i' and release the mandrel.

lVhen the reamer is lowered in the well and the bits carried below the shoe at the bottoni of the casing so as to be released, the mandrel 31 is tree to be impelled up ward by its compressed spring 15. The teusion exerted on the mandrel causes the shoulders 2() to ride outwardly and upwardly over the eurved end of the tongue 13. The lower corners of the tongue are given a greater curvature7 so that the shoulders 20 will more readily ride off the same. As the shoulders 2li ride ofi the rounded eorners of the tongue. the channels 4T are entered by the perpendicular edges of the tongue, whereby the bits are guided as they are ex"- panded. The mandrel through its cross head 32 pulls the Shanks 19 into the dovetail sockets, the ribs 26 sliding in the grooves 1-l and the splines 17 entering theI sumps 4S.

lt is pointed out that the tapering sur faces of the channels will engage the tapering sides of the tongue; while the tapering Shanks will engage the tapering sockets and the splines` wedge in the sunips. This eontact ot' inclined and tapering surfaces will cause the parts to wedge togeher. whereby a tight tit will be had and by leaving a clearance between transverse contacting surfaces. wear is taken up by the parts wedging together. Should the parts become badly worn the bits may be removed, heated and then driven on the splines and the play taken up by tightening the bolt 35.

As the bits come to rest in the sockets the shoulders 22 engage the shoulders "16 of the reamer body and the shoulders 2() engage the lower end of the reamer body. It will be seen that the shoulders 20 and 22 and` the top of the shanks 19 give transverse bearing areas of a large amplitude and considerably more than is present in other reamers now in general use: and thus end thrusts are not only sustained lvtlie wedging surfaces but by the transverse surfaces which make an extremely strong and dur-- able reamer.

Attention is called to the tongue lil dis posed between the expanded hits and engaging in the channels 4,?. ily thisarrangement theliits are braced against collapsing inwardly when in operation as well as against lateral and torsional strains. Each bit is also braced against radial strains liv the dove-.tail shape of the Shanks and the splines l? and against transverse strains by bosses 2l and the tongue lil. lt will be seen that the hits are virtually supported against strains in all direi-tunis and will undergo extremely heavy duty without breaking down.

It is pointed out that the cross-head IPv2 gives a large bearing surface for the seats l-l of the slianlts and the weight oi' the slianks is carried on the head and not on the bolt a rery strong and duralil` :uur struction. It will be seen that should bolt be broken the shanlts cannot be i engaged from the mandrel until the bits i..V far enough to disengage the ribs it? iro-in .the grooves ll. To pi'erent this disengagement however and lo provide a safety leature so that a bit cannot be lost in tru; all unless broken through the boss4 2l or lower down,\l provide a recess 5t? in tbe inner lare for engaging a lug (lli on each side oi' the tongue. v

This application is a continuation in part of my application tiled (letolier flrd. lill?. Serial Number 392.641, and allowed ile cember Bist. 191),

Vlihat l elaini, is:

l. In an ulnlerreinner, a remuer body. an integal central tongue depending at the lower end of the body. said body having vertiral sockets at its lower end on ear-ll side of the tongue` bitsy disposed at the ve tical edges of the tongue and haring po overlapping the sides of the tongue. Shanl. extending upwardly l'roni the bits on the, sides of the tongue and engaging in the sockets, and spring inipelled means mounted in the bod-y for pivotally supporting said bits. said means being eonnected with the Shanks and acting to draw the Shanks into the sockets for expanding the bits. 2. ln an underreamer, a reanier body. an integral central tongue depending at the lower end of the body. said body having vertical sockets on each side of the tongue and said sockets having enlargements at the sides of the tongue.y bits disposed at the vertical edges of the tongue and having portions overlapping the sides of the tongue. Shanks extending upwardly from the bits on the sides of the tongue and engaging in the sockets, Vertical projections on the Shanks engaging in the enlargements of the sockets for holding said shanks againstloutward displacement, said shanks sliding vertically 1n the sockets, and spring .actuated means located in the reamer body and pivotally supporting the Shanks for expanding` 5 the bits.

3. In an underreamer, a reamer body, an

integral central tongue depending at the located in the reamer body and ivotally supporting the Shanks for ex an ing the bits, and means co-actin ietween the tongue and the bits for limiting the downward displacement of the shanks to prevent their disengagement from the sockets.

4. In an underreamer, a reamer body, an integral central tongue depending at the lower end of the body, said bodyhaving radial dove-tail sockets extending vertically on each side of the tongue, and spring sustained bits havin dove-tail Shanks fitting vertically in sai sockets, said bits having vertical channels receiving the vertical edges of the tongue, said tongue being dis- .posed between said bits.

5. In an under-reamer, a reamer body, a

longitudinally projecting relatively thin wedge-shaped tongue located centrally at the lower end of the body and having opposed sides converging downwardly, and

bits pivotally and resiliently connected with the body having vertical `wedge-shaped channels conforming to the taper of the tongue, said channels receiving t e edges of the bits which wedge on said tongue when expanded.

6. In an underreamer, a reamer body, an integral central tongue depending at the lower end of the body, said body having vertical sockets at each side of the tongue and being stepped at its lower end, a pair of bits having stepped shoulders co-aeting with the stepped lower end of the body, said bits having vertical channels receiving the edges of the tongue, Shanks slidably and pivotally engaging in said sockets of the body, means located in the body and pivotally 60 connected with the Shanks.

7. In an underreamer, a reamer body, a tongue at the lower end of the body, said body having vertical sckets at its lower end, a pair of bits having channels for re- 65 ceiving the tongue and swinging under the and spring actuated contracting tongue when lowered, Shanks extending upwardly and slidable in the sockets, spring actuated means for drawing the bits upwardly, whereby they are expanded by the tongue which is received in the channels, said spring means being pivotally connected with the s anks, and a spring actuated latch device carried in the reamer body for holding the spring retracting means in restraint, whereby the bits may be collapsed under the tongue.

8. In an underrreamer, the combination of a reamer body, an integral tongue depending at the lower end of the body, said tongue having a vertical slot, said body having vertical sockets on each side of the tongue, downwardly extending splines on each side of the tongue, a pair of bits having vertical channels receiving the edges of the tongue and provided with sumps receiving the splines, Shanks extending upwardly from the bits and slidably engaging in the sockets, a mandrel disposed within the reamer body and having its lower end in the slot'of the tongue and pivotally engaging the shanks, and a coiled spring connected with the mandrel for impelling the latter upwardly in the reamer body to drawthe Shanks into the sockets and the sumps about the splines, the bits being movable downwardly against the tension of the spring and collapsible under the tongue, the bits being withdrawn from the splines when collapsed.

9. In an underreamer, the combination of a reamer-body, an integral tongue dcpend- 10o ing from the lower end of the body und having a vertical slot, vertical sockets tapered upwardly in the body on cach side of the slot of the tongue, a pair of bits having shoulders engaging under the tongue when said bits are collapsed, said bits having vertical channels receiving the vertical edges of the tongue when said bits are expanded, tagering shanks extending upwardly from the its and engaging in the sockets ot' the body. 110 a mandrel having pivotal connection ut its lower end with the shanks through the slot of the tongue, and :i coiled spring engaging the mandrel for impelling the same up- Wnrdl to draw the Shanks into the sockets, whereby the tongue expands the bits.

10. In an underreamer, the combination of a reamer-body, an integral tongue depending from the lower end of the body und aving a vertical slot, vertical sockets tapered upwardly in the body ou each side of the slot oi the tongue, a pair of bits having shoulders engaging under the tongue when said bits are collapsed, said bits having vertical channels receiving thc verticaledges of the tongue when said bits are expanded, tapering Shanks extending upwardly from the bits and engaging in the sockets of the body.

a mandrel having pivotal connection at its lower end with the Shanks through the slot of the tongue, a coiled spring engaging the mandrel for impelling the same upwardly to draw the shanks into the sockets, whereby the tongue expands the bits, a spring pressed latch engaging the mandrel for holding the saine in a downward position when the bits are collapsed, and means in the body for automatically withdrawing the latch and releasing the mandrel when carried below the well casing shoe.

1l. In an underreanier` areamer body, a tongue depending centrally from the lower end of the body and having a vertical slot, a pair of bits mounted on each side of the tongue and having shoulders engaging under the tongue when collapsed, the body having tapering sockets extending vertically on each side ofthe slot, tapering Shanks extending upwardly and slidably engaging in the sockets, said Shanks having side recesses, a mandrel slidable in the reamer body a cross-head on the mandrel extending through the slot of the tongue and pivotally mounted in the side recesses for supporting the Shanks, means for confining the shanks on the cross-head, and a coiled spring in the reamer body exerting an upward tension on the mandrel.

12. In an underreamer, a reamer body, a tongue depending centrally from the lower end of the body and having a vertical slot, a pair of bits mounted on each side of the tongue and having shoulders engaging under the tongue when collapsed, the body having tapering sockets extending vertically on each side of the slot, tapering sh'anks extending upwardly and slidably engaging in the sockets, a mandrel slidable in the rearner body, a cross-head `on the mandrel extending through the slot of the tongue and pivotally supporting the shanks, a bolt passing through the cross-head and the Shanks, said bolt having its ends countersunk in the Shanks and being fastened against rotation, and a coil spring in the rearner body exerting an upward tension on the mandrel.

13. In an underrearner, the combination of a pair of swinging bits, Shanks extending upwardly from the bits, ribs on each side of the bits, a reamer body having an integral tto ue depending from its lower end provide with a. vertical slot, a mandrel bore in the body above the slot and oonnected therewith, the body having grooves on each side of the tongue at each side of the slot for receiving the ribs of the Shanks and also having radial recesses extending from the grooves for receiving the Shanks, a mandrel in the bore ot the body having a cross-head in the slot of the tongue, said cross-head being pivotally connected With the Shanks, and a coiled spring supported in the bore of the body and surroundin the mandrel and supporting the same, th

1,3es,9e1

body having a transverse opening for admitting a tool for depressing the mandrel.

14 n an underreainer, the combination with a reamer bod having a tongue depending from its, ower end and tapered sockets on each side of the tongue, said tongue having its lower end rounded, and a spring impelled mandrel within the body, of a pair of bits each having a cutter at its lower end and com )rising a bit body and a shank, each bit v"ody lhaving a vertical channel on its inner side for receivin a vertical edge of the tongue, the Shanks s idably engaging in sockets of the reamer bod and pivotally supported by the inandrel each shank boing out off at one upper. corner and notchel on the opposite side to permit the shank and bit bod to swing when the bits are lowered, said it bodies each having a shoulder engaging under the rounded end oi the tongue when the bits are collapsed l. A bit for an underreamer including, a laterally extending wing, an upright shank above the wing, a boss at the intersection of the Wing and shaiik, and a web connecting the inner side of the Wing with the bottom of the shank, the Wing having a vertical channel in its inner side, the boss having a sump extendin upwardly, in combination with a reamerplbody receiving and pivotally supporting the shank and having a tongue engaging the channel and a spline engaging in ythe sump.

16. In an underreamer, the combination of a reanier body, a central tapered tongue extending downwardly from the lower end of the body and provided with a vertical slot, the reamer body having a main bore connected with the slot and also provided with dove-tail sockets extending vertically on each side of the slot, said bod being shouldered above its lower end an exposing the side of the tongue, a spline on the side of the tongue extending downwardly from the shoulder, a mandrel extending from the main bore of the reamer body to the slot of the tongue, a cross-head on the lower end of the mandrel Within the slot, a pair of bits having dove-tail Shanks extend ing upwardly into the sockets and pivoted on the cross-head, said bits having channels receiving the tongue, the lower end of the tongue being rounded, the bits being coilapsible under the rounded end of the tongue, said bits having sumps receiving the splines when the bits are expanded, and a bit expanding spring encircling the n ndrel within the main bore of the rearner bod f.

`17. In an underreamer, a reamer bo y, a central longitudinal tongue extending from one end of the bod ,said body having sockets in its sides, whic sockets taper both radially and longitudinally, bits located at opposite sides of the tongue and having shoulders adapted to be positioned under the lower end of the body when the bits are in expanded position, pering shanks extending from correspondingly tathe bits and slidable in the sockets, a pivotal support or the Shanks,

and means for moving the pivol the reamer the bits are moved around tongue and expanded.

central longitudiml tongue extending from one end of the body,

sockets in per both r located at said body having its sides which sockets taadially and longitudinally, bits opposite sides of the tongue and having shoulders adapted to be po-` sitioned under the lower end of the body when the bits are in expanded position, correspondingly tapering shanks extending from the bits and slidable in the sockets, a

pivotal support for `for moving the pivotal of the rearner body, whereby t nally are moved and expanded,

the Shanks, and means support lon itudie bits around the edges of the tongue said bits, said tongue and said body having tapering contacting surfaces.

19. A bitfor an underreamer including, a

laterally extending Wing, an upright s hank above the wing, a b ss at the intersection of the wing and shan and a web connecting the inner side of the wing with the bottom of the shank, in combination with a reamer body receiving and pivotally supporting the shank and having a relatively fixed expanding element disposed at a right angle to said wing and engaged by the inner bit an upright of the s side of the 2.0. A bit for an underrcainer, including shank, a Wing at the lower end ank extending laterally beyond one side only of the shank, whereby the shank is oset laterally from the center of the wing,

' in combination with a body receiving and pivotally supporting the shank and having a relatively ixed expanding clrif'ecrt dis-4 posed, at a right angle to said vim,A

and enr gagedrby the inner portion of the bit.

2l. In an underrvarner, a body with a longitudinally` extending tongue and longitudinally extending sockets, longitudi` nal YShanks slidably mounted in the sockets upon opposite sifflet ci the tongue and inl.pted to swing 4 parallel w1 carried by Yin planes substantially th the sides of the tongue. hits the Shanks and arranged at sub- 'posite sides, longitudinal sbanks adapted to move longitudinally within the longitudinal sockets and to turn in planes substantially parallel with said opposite sides of the tongue, bits carried by the Shanks and adapted to engage with the edges of the tongue and be expanded thereby, said bits swinging away from the edges of the tongue, and means to effect the longitudinal movement of the shanks.

23. In an underreamer, a body having a longitudinal tongue provided with a longitudinal opening, said body having longitudinal Sockets, Shanks slidable within the sockets, each shank being provided upon its inner face With a cylindrical recess, a ma1idrel within the body and having a crosshead disposed within the longitudinal opening of the tongue with the ends of the crosshead projecting laterally beyond the tongue and pivotally seated within the cylindrical recesses, bits carried by the Shanks and engaging said tongue` and means to move the Shanks longitudinally.

24. In an underreanier, a body having a tongue and longitudinal sockets` the end of the body adjacent each longitudinal socket being arranged one above the other in stepped relation, Shanks mounted within the sockets, bits carried by the shanks, each bit having its upper end adapted to engage beneath the lower end of the body. a boss carried by the upper end of the bit and projecting above the same to engage bcurafb tbc upper cnd of tbc body whereby tl-foiuis o? engagement between tbc bit and its l-:ifzf nidi tbc said lower and upper ends are arranged to break joint, thc bits bcing expanded by engagement with said tongue, and ini-ans to inovc the Shanks longitudinally.

ln testimony whereof I allix my signature.

GUSTAVUS A, MONTGOlvIICltY.

llO 

